Enhancements to computer performance have made it possible to run multiple virtual computers (hereinafter, virtual machines) on a physical computer. The virtual machine executes a variety of processing by booting up an operating system that has been installed in a virtual storage device (hereinafter, the virtual hard disk drive).
Meanwhile, technology for acquiring a writable snapshot on a file system is known (Patent Literature 1). A snapshot is a still image of data at a certain point in time.
In accordance with the writable snapshot technology, difference data is generated as a result of writing to the snapshot. The difference data is stored in a separate storage area from the storage area in which the snapshot was created. The difference data storage destination is changed to this separate storage area.
In addition, technology for making the logical volume storage contents of two storage apparatuses match up is also known (Non-Patent Literature 1). This technology is premised on a case in which a copy pair is formed between a local volume A in a local storage server and a remote volume A in a remote storage server, and a copy pair is formed between a local volume B in a local storage server and a remote volume B in a remote storage server. In this technology, in a case where a Flash Copy is carried out from local volume A to local volume B, a Flash Copy is also carried out between remote volume A and remote volume B.